Patent Application
20060236456
Embodiments of the present invention relate to a transport device and methods, and particularly to reducing the effects and damage to items or patients being transported as a result of certain energy inputs to the transport device and resulting acceleration-related inputs to the patient or item.
Patient transport devices, often referred to as gurneys, stretchers, and the like, have long been used to transport people having injuries from one place to another, such as from an accident site to a hospital, or from hospital to hospital, etc. In addition to being themselves mobile, many patient transport devices may be adapted for use with a number of different transport vehicles, including ambulances, airplanes, helicopters, snow machines, and the like. When these vehicles are transporting patients from one location to another, they inevitably encounter disturbances such as bumps, potholes, turbulence, or other inconsistencies in the transport medium, which in turn causes a sudden change in position of the patient transport device. This abrupt change in position is transmitted to the patient, and can cause the patient to be subject to accelerations in various directions.
The magnitude of these external energy inputs and the resulting accelerations of the patient in different directions can have a severe and oftentimes detrimental impact on the patient being transported, particularly if the patient has head, neck, and/or spinal trauma, for example. Any undue energy input cannot only further aggravate an existing injury, but may ultimately result in death.
Another particularly susceptible category of patients are neonatal patients. Oftentimes being several weeks if not months premature, the biological systems within the neonatal patient, particularly the vascular system, has not fully developed and is extremely susceptible to damage. Even the smallest amount of vibrations and accelerations transmitted to the neonatal patients through the patient transport device during transfer can have traumatic impacts. One serious concern, but not the only serious concern, is intraventricular hemorrhage, which is where blood vessels in the brain rupture. Because the blood vessels in the brain of neonatal patients are underdeveloped (i.e., very thin and not prepared for significant stress), the vibrations and the accelerations of the patient as a result of the vibrations may cause the blood flowing through those vessels to be inclined to suddenly stop and/or change directions. Since this is not possible due to the continuous flow of blood through the system, an outward pressure is applied to the underdeveloped vessel causing them to fatigue and/or rupture.
Current patient transport devices often have a number of inherent passive energy and vibration absorption systems, such as a mattress, rubber in the wheels of the transport device, and when a vehicle is used, for example, the vehicle's suspension. Some patient transport devices may even have additional passive systems, such as shock absorption devices to further absorb various energy inputs. These devices may not provide an acceptable energy and vibration absorption capability for the susceptible patients described above. While the passive systems may ultimately absorb external energy inputs and vibrations, they are often too slow, may initially amplify the accelerations resulting from certain energy inputs, and cannot adequately attenuate the acceleration encountered by the patient.
Accordingly, it is desirable to develop a patient transport device that somewhat decouples the patient from the transport device such that the external energy inputs, such as vibrations, impulse inputs, and step inputs encountered by a patient transport device, will be minimized and any accelerations of the patient as a result will be reduced so as to reduce the creation and/or aggravation of existing injuries.
Embodiments of the present invention will be readily understood by the following detailed description in conjunction with the accompanying drawings. To facilitate this description, like reference numerals designate like structural elements. Embodiments of the invention are illustrated by way of example and not by way of limitation in the figures of the accompanying drawings.
In the following detailed description, reference is made to the accompanying drawings which form a part hereof wherein like numerals designate like parts throughout, and in which is shown by way of illustration embodiments in which the invention may be practiced. It is to be understood that other embodiments may be utilized and structural or logical changes may be made without departing from the scope of the present invention. Therefore, the following detailed description is not to be taken in a limiting sense, and the scope of embodiments in accordance with the present invention is defined by the appended claims and their equivalents.
Embodiments of the present invention relate to the reduction of external energy inputs, such as vibrations, step, and impulse inputs, that are transmitted to something being transported, such as a patient, through the transport device, by implementing an Active Control System (ACS). The ACS may include both passive suspension components and an active controller adapted to input energy into the system, wherein they work in cooperation to reduce the impact of external energy inputs on a patient or item being transported. Embodiments in accordance of the present invention may include a controller that may input a force in a direction required to cause the patient support to track back to a position that is a predetermined distance away from a portion of the frame of the patient transport device. This action may have the overall effect of reducing the acceleration of a patient as a result of the external energy input. Embodiments of the present invention may include altering the magnitude and direction of the force input by the controller based on the direction and magnitude of the external energy input.
Active control systems in accordance with embodiments of the present invention may be configured to reduce the amount and/or effect of an external energy input to the transport device that may be transmitted to the item or patient being transported. A number of different external energy inputs may be encountered, including vibrations (high-frequency, low-magnitude input) that may be caused for example rolling a gurney over rough surfaces such as aggregate, elevator threshold, and the like. Another external energy input may be caused by a step input, which may occur when an ambulance hits a curb, for example, such that the overall position of the patient transport device steps up or down from a first elevation to a second elevation. Yet another external energy input may be caused by an impulse input, which may result from an ambulance hitting a speed bump or pothole, for example, where the patient transport device is temporarily displaced from a first elevation to a second elevation and then returns to the first elevation.
In one embodiment, the ACS 21 may include guide members 30 configured to positionally couple patient support 13 to support reference 12 and allow limited movement in one or more desired directions. While the degrees of movement may be enabled as desired, in the illustrated embodiment, guide members 30 are configured to allow for linear movement of the patient support 13 vertically with respect to the substantially horizontal position of the support reference 12.
The ACS 21 may also include one or more passive suspension devices 18 actively coupled between the patient support 13 and the support reference 12. Passive suspension devices 18 may include a spring 32 configured to absorb energy stemming from the positional change of the support reference 12 caused by the external energy input. Passive suspension devices 18 may also include one or more dampeners 34 configured to dampen the absorption and/or release of energy through springs 32. While the passive suspension devices illustrated show separate components, such devices may be a single component, and may include other spring mechanisms such as elastomers.
Given an external energy input to the support reference 12, which may be caused, for example, by the patient transport device 10 crossing a sliding door threshold or encountering a curb, the magnitude of the energy input may be initially at least partially absorbed by the one or more passive suspension devices 18, and thus result in a reduced energy input being conveyed to the patient support 13. This may in part result in a decrease in the position, velocity, and/or acceleration of the patient support 12 as a result. Passive suspension devices 18 may include a variety of energy absorption and dampening devices and/or vibration/shock absorption devices, including, but not limited to, springs and dampers, electromagnetic fields, pneumatic systems, and the like.
The ACS 21 may also include a force generator 20 controllably coupled between the patient support 13 and the support reference 12. Force generator 20 may be adapted to input a second energy or force into the system aimed at offsetting some or all of the effects (positional, velocity, and acceleration) on the patient support 13 that could result due to the external energy input. Input of the second energy by force generator 20 may help to counteract the positional movement of the patient support 13, and in turn reduce the acceleration observed by the patient as a result of the external energy input. The direction and magnitude of the second energy input may be varied as required to minimize the positional change of the patient support with respect to the support reference 12.
As illustrated in
When an external energy is applied to the system, a step input in the illustrated case of
Once the energy stored in the springs of the passive suspension components, along with the second energy input F1, begins to move the patient support 13 vertically upward with respect to the support reference 12, a positive velocity of the patient support will result. The patient support may also move from P1′ to P2″, resulting in a separation distance D3, as illustrated in
This cycle may repeat until the velocity of the patient support 13 is substantially zero with respect to the support reference 12 and the separation distance is substantially back to the static distance of D1. As shown by
As can be seen from
Testing was also conducted where the energy input was the result of an impulse input, such as hitting a speed bump in an ambulance or turbulence in an airplane. Again, there was found to be a significant reduction in the position movement and acceleration of the patient. Likewise, the accelerations attenuated more rapidly than current systems not using ACS.
The force generator 20 may be configured in a variety of ways that may, allow for the controllable supply of a second energy input into the system. In one embodiment, for example, one or more rotary motors may be used in conjunction with a rack and pinion system to control the magnitude and direction of the second energy input, as shown in
Embodiments of the present invention may also include sensors 19 that may be adapted to sense the direction and magnitude of a response characteristic of the patient support 13 as a result of the external energy input. Sensor 19 may be in communication with a controller 23 adapted to apply a control law based on an input from sensor 19. Controller 23 may send a signal to force generator 20, such that the force generator may input a second energy of a magnitude of and direction appropriate to offset some of the effects of the external energy input, and ultimately reduce the acceleration of the patient support and, as a result, the patient. Sensor 19 may be, for example, a position, velocity, and/or acceleration based sensor.
The ACS in accordance with embodiments of the present invention may be a closed loop system employing negative feedback. Generally, when there is a disturbance to the system, e.g., an external energy input, the system dynamically responds, the response is sensed/measured, the force generator is sent a signal and the system responds dynamically to the second energy input, thus changing the sensed/measured characteristic. The total system response is again measured by the sensor and the force generator is again sent a signal causing the system to again respond. This is repeated until the system returns to an equilibrium state, e.g., zero input to the sensor measuring the response characteristic.
In one embodiment, the magnitude and direction of the second energy input may be determined and controlled via a negative feedback control loop, an example of which is illustrated in
Sensor 19 may be adapted to sense Y1 and generate a representative signal SV, such as a voltage or current that characterizes the response characteristic being sensed. A controller 23 may be in electrical communication with the sensor 19 and adapted to receive the sensor signal SV. The controller may compare the sensor signal SV to a reference point to determine the variation of the response characteristic from a desired state. For example, the reference point may be a specific position of the patient support relative to the rest of the transport device; or a zero velocity indicating that the patient support is not moving relative to the rest of the transport device. The controller may then process the sensor signal using a predetermined control law, and generate a control signal Sc. The force generator 20, which may be in electrical communication with the controller, may be adapted to receive the control signal SC, and generate a second energy input F. Second energy input F will result in the system response GSYS
In one embodiment of the present invention, sensor 19 may be a velocity-based sensor adapted to measure the velocity of the patient support 13. The velocity sensor may be may be coupled to the controller, such that when a negative velocity is sensed, for example, the controller 17 generates a control signal to the force generator 20 to generate a force of a certain magnitude in positive direction to offset the negative velocity. The sensor may continue to measure the velocity of the patient support and generate sensor signals representing the response characteristic.
Periodic generation of sensor signals and thus generation of control signals may cause the force generator to variably alter the direction and magnitude of the second energy input until the velocity of the patient support is substantially zero. This periodic measurement of sensor signals and subsequent generation of appropriate control signals that are in turn sent to the force generator creates a feedback loop. This feedback loop constantly adjusts the force generated as the response characteristic changes over time. The control law is formulated to return the system to its original state (i.e., the state prior to the external input YR acting on the system) as quickly as possible while minimizing the accelerations transmitted to the patient support as well as the overall movement of the system. This may in turn result in quicker attenuation of the accelerations of the patient support than would normally occur with only passive suspension components.
In one embodiment, where the sensor is a position sensor, and the external energy input is a step input directed to the patient transport device (e.g., hitting a curb) the support reference dynamically responds by raising to a second position. The position sensor will sense such second position and generate a sensor signal representative of the new position. The controller may process the signal using a control law and generate a corresponding control signal that will cause the force generator to provide a second energy input in the system to try and maintain a desired distance between the support reference and the patient support, while minimizing the relative velocity and overall acceleration of the patient support.
The ACS 321A of
Embodiments of the present invention may be used with a variety of different patient transport device configurations, including those adapted for transport in vehicles configured for transportation over the roadways, such as ambulances, transportation via the airways, such as helicopters and airplanes, and/or vehicles adapted for other surfaces such as snow, rough terrain, and the like. Embodiments of the present invention may also be used with other transport devices, where the accelerations transmitted to an item being transported need to be reduced.
The active control system in accordance with embodiments of the present invention may be operated by a power source that is portable (e.g., battery powered) or may otherwise be adapted to interface with electrical system on board the transport vehicle. Further, the ACS may be adapted to run on either DC or AC systems.
Although certain embodiments have been illustrated and described herein for purposes of description of the preferred embodiment, it will be appreciated by those of ordinary skill in the art that a wide variety of alternate and/or equivalent embodiments or implementations calculated to achieve the same purposes may be substituted for the embodiments shown and described without departing from the scope of the present invention. Those with skill in the art will readily appreciate that embodiments in accordance with the present invention may be implemented in a very wide variety of ways. This application is intended to cover any adaptations or variations of the embodiments discussed herein. Therefore, it is manifestly intended that embodiments in accordance with the present invention be limited only by the claims and the equivalents thereof.
